Light-emitting diode

ABSTRACT

The present invention relates to a light-emitting diode (LED). The LED comprises an LED die, one or more metal pads, and a fluorescent layer. The characteristics of the present invention include that the metals pads are left exposed for the convenience of subsequent wiring and packaging processes. In addition, the LED provided by the present invention is a single light-mixing chip, which can be packaged directly without the need of coating fluorescent powders on the packaging glue. Because the fluorescent layer and the packaging glue are not processed simultaneously and are of different materials, the stress problem in the packaged LED can be reduced effectively.

FIELD OF THE INVENTION

The present invention relates to a light-emitting diode, andparticularly to a light-emitting diode capable of mixing light.

BACKGROUND OF THE INVENTION

A light-emitting diode (LED) is a light-emitting device manufactured bysemiconductor materials with two electrodes. The light-emittingprinciple of the LED is that by applying a voltage between theelectrodes and supplying an extremely small current, excess energy canbe released in the form of light via the recombination process ofelectrons and holes. The LED is different from an incandescent bulb inthat the former is luminescent with advantages of low power consumption,elongated lifetime, no warm-up time, and fast response. In addition,because the LED is small, vibration tolerable, and suitable for massproduction, it is easy to be manufactured in an extremely tiny or amatrix form in accordance with application requirements. Currently, theLED is widely applied to indicator and display apparatuses ofinformation, communication, and consumer electronic products, and hasbecome a dispensable and important device in daily lives.

Presently, most LEDs are coated with fluorescent powders in the packagesduring the packaging process. Thereby, the stress problem will occur inthe packages. The present invention provides an LED in a singlelight-mixing chip, which can be packaged directly, and hence reducingeffectively the stress problem as described above.

SUMMARY

An objective of the present invention is to provide a light-emittingdiode (LED), which can expose metal pads for the convenience ofsubsequent wiring and packaging processes.

Another objective of the present invention is to provide an LED, whichcan provide a single light-mixing chip for direct packaging and reducingthe stress problem in the packaged LED.

In order to achieve the objectives described above, the presentinvention provides an LED, which comprises an LED die, one or more metalpads, and a fluorescent layer. The LED die includes two electrodes. Themetal pads are set on the electrodes of the LED die. The fluorescentlayer is set on the LED die. Beside, the fluorescent layer does notcover the metal pads completely. Instead, the metal pads are exposed forthe convenience of subsequent wiring and packaging processes. Thefluorescent layer converts directly partial or all of light with a firstwavelength produced by the LED die to light with at least a secondwavelength.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a structural schematic diagram according to a preferredembodiment of the present invention;

FIG. 2 shows a flowchart according to a preferred embodiment of thepresent invention;

FIG. 3 shows a flowchart for forming an LED die according to a preferredembodiment of the present invention;

FIG. 4A shows a structural schematic diagram according to anotherpreferred embodiment of the present invention;

FIG. 4B shows a structural schematic diagram according to anotherpreferred embodiment of the present invention;

FIG. 5 shows a structural schematic diagram according to anotherpreferred embodiment of the present invention;

FIG. 6 shows a flowchart according to a preferred embodiment of thepresent invention;

FIG. 7 shows a structural schematic diagram according to anotherpreferred embodiment of the present invention; and

FIG. 8 shows a flowchart according to a preferred embodiment of thepresent invention.

DETAILED DESCRIPTION

In order to make the structure and characteristics as well as theeffectiveness of the present invention to be further understood andrecognized, the detailed description of the present invention isprovided as follows along with preferred embodiments and accompanyingfigures.

FIG. 1 shows a structural schematic diagram according to a preferredembodiment of the present invention. As shown in the figure, the presentembodiment provides a light-emitting diode (LED) 1, which comprises anLED die 10, one or more metal pads 12, and a fluorescent layer 16. TheLED die 10 includes two electrodes 107. The number of the metal pads 12according to the present embodiment is two. The two metal pads 12 areset on the two electrodes 107, respectively. The fluorescent layer 16 isset on the LED die 10. In addition, the fluorescent layer 16 does notcover the two metal pads 12 completely. Instead, the metal pads 12 areexposed for the convenience of subsequent wiring and packagingprocesses. The fluorescent layer 16 converts partial or all of lightwith a first wavelength produced by the LED die 10 to light with atleast a second wavelength for producing light mixing. The LED 1 providedaccording to the present embodiment is a light-mixing chip, which can bepackaged directly without the need of coating fluorescent powders on thepackage. The thickness of the fluorescent layer 16 is greater than 30μm. The materials of the fluorescent layer 16 include fluorescentpowders and an organic polymer material. The fluorescent powders arechosen from the group comprising red fluorescent powders, greenfluorescent powders, blue fluorescent powders, and the combination ofthe fluorescent powders described above.

The LED die 10 described above further comprises a first semiconductorlayer 101, a light-emitting layer 103, and a second semiconductor layer105. The light-emitting layer 103 is set on the first semiconductorlayer 101; the second semiconductor layer 105 is set on thelight-emitting layer 103; the metal pads 12 are set on the electrodes107. When the first semiconductor layer 101 is P-type, the secondsemiconductor layer 105 is N-type. Alternatively, when the firstsemiconductor layer 101 is N-type, the second semiconductor layer 105 isP-type.

FIG. 2 shows a flowchart according to a preferred embodiment of thepresent invention. As shown in the figure, in contrast to FIG. 1, whichshows an LED 1, the present figure shows a method for manufacturing theLED 1. To manufacture the LED 1, the step S10 is first executed forforming an LED die 10, which includes two electrodes 107. Referringtogether to FIG. 3, the method for forming the LED die 10 comprises thestep S101 forming a first semiconductor layer 101; the step S103 forminga light-emitting layer 103 on the first semiconductor layer 101; andfinally the step S105 forming a second semiconductor layer 105 on thelight-emitting layer 103.

After the step S10 is completed, the step S12 is executed for formingone or more metal pads 12 on the two electrodes 107 of the LED die 10.Next, the step S14 is executed for forming a fluorescent layer 16 on theLED die 10. The fluorescent layer 16 does not cover the metal pads 12completely. Instead, the metal pads 12 are left exposed for theconvenience of subsequent wiring and packaging processes.

For forming the fluorescent layer 16 on the LED die 10, glue dispensing,spaying, or pouring methods are applied. For avoiding the fluorescentlayer 16 from covering the metal pads 12 completely during the formingprocess of the fluorescent layer 16, prior to forming the fluorescentlayer 16 on the LED die 10 using the glue dispensing, spaying, orpouring methods, a mask is used on the metal pads 12. The mask can maskthe metal pads 12 and expose the location to form the fluorescent layer16. Besides, the mask is manufactured by lithography or byscreen-printing using organic polymer materials such as photoresist. Theglue ratio in the glue dispensing, spaying, or pouring methods iscontrolled according to the photoelectric properties of the LED die 10.

FIGS. 4A and 4B show structural schematic diagrams according to otherpreferred embodiments of the present invention. As shown in the figures,according to the present embodiments, two LED structures are provided.The difference between the present embodiments and the one describedabove is that, according to the present embodiments, the shape of thefluorescent layer 16 can be changed by etching. The shapes of thefluorescent layer 16 can be trapezoidal or upside-down trapezoidal.

FIG. 5 shows a structural schematic diagram according to anotherpreferred embodiment of the present invention. As shown in the figure,the present embodiment provides an LED 1 comprising an LED die 10, oneor more metal pads 12, a dielectric layer 18, and a fluorescent layer16. The LED die 10 includes two electrodes 107. The metal pads are seton the electrodes 107 of the LED die 10. The dielectric layer 18 is seton the LED die 10, and is located on the periphery of the metal pads 12.The fluorescent layer 16 is set on the dielectric layer 18, and islocated on the periphery of the metal pads 12. The fluorescent layer 16converts partial or all of light with a first wavelength produced by theLED die 10 to light with at least a second wavelength for producinglight mixing. In addition, the fluorescent layer 16 does not cover themetal pads 12 completely. Instead, the metal pads 12 are exposed for theconvenience of subsequent wiring and packaging processes. The LED 1provided according to the present embodiment is a light-mixing chip,which can be packaged directly without the need of coating fluorescentpowders on the package. Besides, the thickness of the fluorescent layer16 is greater than 30 μm. The LED die 10 further includes a firstsemiconductor layer 101, a light-emitting layer 103, and a secondsemiconductor layer 105.

FIG. 6 shows a flowchart according to a preferred embodiment of thepresent invention. As shown in the figure, in contrast to FIG. 5, whichshows an LED 1, the present figure shows a method for manufacturing theLED 1. To manufacture the LED 1, the step S10 is first executed forforming an LED die 10. Then the step S12 is executed for forming one ormore metal pads 12 on the electrodes 107 of the LED die 10. Next, thestep S13 is executed for forming a dielectric layer 18 on the LED die10. Finally, the step S14 is executed for forming a fluorescent layer 16on the dielectric layer 18. The fluorescent layer 16 does not cover themetal pads 12 completely. Instead, the metal pads 12 are left exposedfor the convenience of subsequent wiring and packaging processes.

For forming the fluorescent layer 16 on the LED die 10, glue dispensing,spaying, or pouring methods are applied. For avoiding the fluorescentlayer 16 from covering the metal pads 12 completely during the formingprocess of the fluorescent layer 16, prior to forming the fluorescentlayer 16 on the LED die 10 using the glue dispensing, spaying, orpouring methods, a mask is used on the metal pads 12. The mask can maskthe metal pads 12 and expose the location to form the fluorescent layer16. Besides, the mask is manufactured by lithography or byscreen-printing using organic polymer materials such as photoresist.

FIG. 7 shows a structural schematic diagram according to anotherpreferred embodiment of the present invention. As shown in the figure,for packaging the LED 1 provided in FIG. 1, the LED 1 is set on acarrier 2. Then, the metal pads 12 are connected by wiring. Finally, usepackaging glue 3 to cover the carrier 2 and the LED 1. The material ofthe packaging glue 3 is organic polymer, and fluorescent powders can befurther contained therein. The organic polymer material of the packagingglue 3 differs from the organic polymer material of the fluorescentlayer described in FIG. 1. In addition, the packaging glue 3 andfluorescent layer 16 are not processed simultaneously. The baking timeof the two is also different, which can reduce the stress problemeffectively produced in the package of the LED 1. Moreover, thepackaging structure according to present embodiment can be applied tothe embodiment of FIG. 5.

FIG. 8 shows a flowchart according to a preferred embodiment of thepresent invention. As shown in the figure, for packaging the LED 1provided in FIG. 1, the step S16 is first executed for setting a carrier2 to the LED 1 and opposite to the fluorescent layer 16. Then the stepS18 is executed for connecting the metal pads 12 by wiring. Finally, thestep S19 is executed for coving the carrier 2 and the LED 1 by packagingglue 3. The packaging method provided according to the presentembodiment can be applied to the LED1 provided in FIG. 5, and will notbe described in detail.

It is known from above that the present invention provides an LED and amethod for manufacturing the same. The characteristics of the presentinvention include that the metals pads are left exposed for theconvenience of subsequent wiring and packaging processes. In addition,the LED provided by the present invention is a single light-mixing chip,which can be packaged directly without the need of coating fluorescentpowders on the packaging glue. Because the fluorescent layer and thepackaging glue are not processed simultaneously and are of differentmaterials, the stress problem in the packaged LED can be reducedeffectively.

Accordingly, the present invention conforms to the legal requirementsowing to its novelty, nonobviousness, and utility. However, theforegoing description is only embodiments of the present invention, notused to limit the scope and range of the present invention. Thoseequivalent changes or modifications made according to the shape,structure, feature, or spirit described in the claims of the presentinvention are included in the appended claims of the present invention.

The invention claimed is:
 1. A light-emitting diode (LED), which is apositive light-emitting type light emitting diode, comprising: an LEDdie; at least two metal pads, set on said LED die, wherein the topsurfaces of said metal pads set on the same plane essentially; afluorescent layer, set on a surface of said LED die and said metal pads;said fluorescent layer located on the periphery of said metal pads andnot covering said metal pads; said metal pads being exposed; said LEDdie comprising a first semiconductor layer; a second semiconductorlayer, a light-emitting layer, a first electrode and a second electrode;said light-emitting layer set on said first semiconductor layer; saidsecond semiconductor layer set on said light-emitting layer; said secondelectrode being completely on top of said second semiconductor layer;said first electrode being completely on top of said first semiconductorlayer; at least one of said metal pads set on said first electrode, andat least one of said metal pads set on said second electrode; thethickness of the fluorescent layer is greater than 30 μm; and at leastpart of light with a first wavelength produced by the LED die isconverted to light with at least a second wavelength by the fluorescentlayer.
 2. The LED of claim 1, wherein the materials of the fluorescentlayer include fluorescent powders and an organic polymer material. 3.The LED of claim 2, wherein the materials of said fluorescent powdersare chosen from the group comprising red fluorescent powders, greenfluorescent powders, blue fluorescent powders, and the combination ofthe fluorescent powders described above.
 4. The LED of claim 1, whereinsaid first semiconductor layer is N-type, and said second semiconductoris P-type.
 5. The LED of claim 1, wherein said first semiconductor layeris P-type, and said second semiconductor is N-type.
 6. The LED of claim1, and further comprising a carrier, set on a side of the LED, and facedto the fluorescent layer.
 7. The LED of claim 6, and further comprisinga packaging glue, set on the carrier, and covers the LED without coatingof fluorescent powders, the metal pads and the fluorescent layer.
 8. TheLED of claim 7, wherein the material of the packaging glue is organicpolymer.
 9. The LED of claim 7, wherein the material of the packagingglue further comprising fluorescent powders.
 10. The LED of claim 1, andfurther comprising a dielectric layer, set between said LED die and saidfluorescent layer.
 11. The LED of claim 1, wherein the shape of saidfluorescent layer is trapezoidal or upside-down trapezoidal.
 12. The LEDof claim 1, wherein a periphery of said fluorescent layer is aligned toa periphery of said LED die.